A source with knowledge of the situation tells The Hollywood Reporter that the 63-year-old Noble, who plays scientist Walter Bishop on the show, is being treated for a sleep disorder. Noble's illness effectively shut down filming on the fifth and final season on Tuesday -- just one day after he was expected to appear on the Television Critics Assn. press tour panel with Anna Torv, Joshua Jackson, Lance Reddick and showrunner J.H. Wyman.

The delay was initially said to be only three days, but sources now say it will be extended to nine shooting days, until about Aug. 7.

Noble's absence was addressed during the Fringe session at the Television Critics Association gathering on Monday, with Wyman telling reporters that the actor was "under the weather."

Filming on the season five premiere began last Wednesday in Vancouver and continued Thursday and Friday. Production on the series was paused Monday so cast members could attend TCA.

Separately, on Tuesday a source confirmed to THR that production had been impacted by co-star Jasika Nicole's car accident, in addition to multiple illnesses in the cast.

The extended delay is not expected to impact the series' Sept. 28 premiere date.

The news comes after castmates and Wyman publicly lauded Noble, who appeared at Comic-Con on July 15, for his work on "Fringe" and discussed his Emmy snub for his complicated performance on the sci-fi series.